Adelaide reservoirs receive inflows during flood watch but dry times are ahead

A flood watch may be in place for Adelaide's Upper Onkaparinga catchment following the first decent rains of winter, but don't get used to it â€” dry times are ahead.

Adelaide's metropolitan reservoirs are at just 54 per cent capacity compared to 73 per cent a year ago, and the city's rainfall is 84 per cent of its usual average level for early August.

It follows a drier-than-average summer and winter, and despite a number of weak cold fronts expected to pass through the state over the next week-and-a-half, the Bureau of Meteorology (BOM) is forecasting a dry second half to August.

"While it's been a wet start to August, overall it's expected to end up with drier-than-average rainfall, and that's looking to be the case in September and probably October as well," senior climatologist Darren Ray said.

Adelaide Hills residents for the moment, however, are enjoying their first real drink of the year, with Lenswood, Lobethal, Bridgewater, Cherryville and Aldgate all recording 100 millimetres or more in the past week.

Even the city got a good drenching, receiving nearly 49 millimetres by Tuesday due to a , and some more rain falling overnight.

Mark Gobbie, SA Water's asset operations and delivery manager, said the rain had come when catchments were saturated enough to allow the water to run off and fill tributaries and send the water downstream into reservoirs.

"This is actually the critical bit, because often you need quite a bit of rain to wet up the very dry catchments so they become saturated and water doesn't soak into the ground," he said.

Of particular benefit has been the 46.5-gigalitre Mount Bold Reservoir, which was only at 16 per cent capacity two weeks ago, but now had filled to just over 34 per cent by Tuesday.

"It's been the sort of thing we've experienced in the past 10 to 15 years; our August, September and spring are generally the more intense rains," Mr Gobbie said.

Reservoir levels down due to dry winter

SA Water's Mount Lofty Ranges storages received only 11 gigalitres of water in the May, June and July period, compared to more than 23 gigalitres it received during the same period last year.

By Tuesday, larger reservoirs like South Para were at 61 per cent, Little Para 37 per cent, Happy Valley 88 per cent, and Millbrook 55 per cent.

"It's probably very important to everyone to realise that OK, it's been a very dry start to the year, but it's not situations we haven't experienced in the past and, certainly, we're onto it," Mr Gobbie said.

"We've got flexibility in our system to supply from different reservoirs; we've got different pipeline systems to be able to transfer water from the River Murray and, of course, we've got the desalination plant as an insurance policy."

He further pointed out the city's water supply was in far better shape, comparatively, to what it was during the Millennium Drought of the 2000s.

"That was a very precarious time for water supply ... we're not close to anything like that at this point of time," Mr Gobbie said.

Mr Ray said the drier conditions could be attributed to cooler-than-average temperatures in northern Australia that had "reduced moisture availability and moisture coming in ahead of the cold frontal systems".

"And we're seeing the sub-tropical region high pressure systems, the systems sitting over Australia, a bit stronger than average and staying further south than what they usually do during autumn and winter," he said.

"It basically means the cold fronts have been staying a bit further south and we've only been getting fairly weak weather activity through this winter so far."

Blue Lake deemed safe for drinking after crash

Meanwhile, Mr Gobbie said residents of Mt Gambier in the state's south-east were once again drinking from Blue Lake after .

He said the mains were switched back from bore water to Blue Lake after extensive testing deemed its water to be "100 per cent" safe for human consumption.

The car remains in the crater lake, however, with an initial plan to remove it using a crane set up on the road above where the car was abandoned.

"The reach from that point creates a crane size that is too big for the road capacity at that point, so we're looking for a number of points around the lake, including our pump station, where we might be able to get a crane in to get it out," Mr Gobbie said.

"We've got containment barriers around the car and all sort of things purely as a precaution but there's been no signs of any leaking oil or fuel or anything like that at this point of time."

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